Hubble himself never accepted that expansion implied a beginning, and expansion is compatible with steady-state models that were taken seriously until the 1960s.

Both true. Expansion alone did not settle the question; the steady-state model was a live alternative until the microwave background killed it, and Hubble stayed agnostic. Hubble’s measurement is cited as the observational turning point: the first evidence that the universe is not static, which is what everyone from Aristotle to Einstein had assumed. The next exhibit, the cosmic microwave background, is what made a hot, dense beginning the mainstream view.